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| United States Patent |
5,019,341
|
|
Niu, ;, , , -->
Niu
, et al.
|
May 28, 1991
|
Method of inhibiting corrosion of metal surfaces in contact with a
corrosive hydrocarbon containing medium
Abstract
Hydrocarbon soluble polyamidoamines prepared from tallowtriamine and/or
tallowtetramine--(methyl)acrylate reactants are effective corrosion
inhibitors for metal surfaces in contact with corrosive hydrocarbon
mediums even under alkaline conditions.
| Inventors:
|
Niu; Joseph H. Y. (Houston, TX);
Edmondson; James G. (Conroe, TX);
Lehrer; Scott E. (Houston, TX)
|
| Assignee:
|
Betz Laboratories, Inc. (Trevose, PA)
|
| Appl. No.:
|
895542 |
| Filed:
|
August 11, 1986 |
| Current U.S. Class: |
422/7; 252/390; 422/14; 422/16 |
| Intern'l Class: |
C23F 011/14 |
| Field of Search: |
422/7,14,16
252/390
|
References Cited
U.S. Patent Documents
| 3397152 | Nov., 1969 | Brown et al.
| |
| 3404165 | Feb., 1970 | Budde et al.
| |
| 3412024 | Feb., 1970 | Stanford.
| |
| 3445441 | Mar., 1970 | Rushton.
| |
| 3554897 | Jan., 1971 | Stanley.
| |
| 3705109 | Dec., 1972 | Hausler | 422/16.
|
| 4131583 | Jan., 1979 | Boerwinkle et al.
| |
| 4240804 | Dec., 1980 | Shields | 44/71.
|
| 4315087 | Feb., 1982 | Redmore | 252/8.
|
| 4339349 | Jul., 1982 | Martin et al. | 422/12.
|
| 4344861 | Aug., 1982 | Levy | 422/16.
|
| Foreign Patent Documents |
| 0087277 | Aug., 1983 | EP.
| |
| 817262 | Jul., 1959 | GB.
| |
| 1109579 | Apr., 1968 | GB.
| |
Other References
Tomah Chemical Product Fact Sheet, TWY #810-280-1401 Sep. 15, 1982.
|
Primary Examiner: Warden; Robert J.
Assistant Examiner: McMahon; Timothy M.
Attorney, Agent or Firm: Ricci; Alexander D., Boyd; Steven D.
Claims
We claim:
1. A method of inhibiting corrosion of metal surfaces in contact with a
corrosive hydrocarbon-containing medium comprising contacting said metal
surfaces with a hydrocarbon soluble polymerization reaction product of a)
a component consisting essentially of tallowtriamine or tallowtetramine or
mixtures thereof and b) an acrylic acid type compound having the
structure,
##STR2##
wherein R is hydrogen or methyl, and R' is methyl, ethyl, propyl,
isopropyl, butyl, amyl, or hexyl.
2. A method as recited in claim 1 wherein said reaction product is added to
said medium in an amount of from about 0.5-500 parts, based upon one
million parts of hydrocarbon.
3. A method as recited in claim 2 wherein said reaction product is added to
said medium in an amount of from about 0.5-50 parts per million parts of
hydrocarbon.
4. A method as recited in claim 1 wherein said polymerization reaction
product is also formed from an additional component (c), wherein (c) is a
member selected from the group consisting of alkylene polyamines having
from about 3 to about 10 amino groups and from about 2-6 carbon alkylene
groups.
5. A method as recited in claim 4 wherein said component (c) comprises
triethylenetetramine.
6. A method as recited in claim 1 wherein (b) comprises methylacrylate.
7. A method as recited in claim 1 wherein the molar ratio of a:b is from
about 1-2:2-1.
8. A method as recited in claim 1 wherein said corrosive hydrocarbon
containing medium is heated to temperatures of between about 100.degree.
F.-1000.degree. F.
9. A method as recited in claim 1 wherein said corrosive hydrocarbon
containing medium is heated to temperatures between about 600.degree.
F.-1000.degree. F.
10. A method as recited in claim 1 wherein said metal surfaces comprise
mild steel.
11. A method as recited in claim 1 wherein said metal surfaces comprise
admiralty brass.
Description
FIELD OF THE INVENTION
The present invention is directed toward the use of certain hydrocarbon
soluble polyamidoamine-type corrosion inhibitors in refinery and/or
petrochemical process systems to inhibit corrosion of metal surfaces under
alkaline conditions.
BACKGROUND OF THE INVENTION
Corrosion has always and is presently a significant problem in the refining
and petrochemical industries by reason of equipment replacement costs and
system downtime associated therewith.
For example, in refinely operation, the crude oil itself commonly contains
corrosive impurities such as salts, sulfur compounds, naphthenic and other
organic acids such as acetic and propionic, nitrogen compounds and
inorganic acids such as hydrochloric acid. Corrosion by crude oil
impurities is accelerated by the high temperatures (e.g., 100.degree.
F.-1000.degree. F.) commonly encountered when oils or petrochemicals are
processed. In many cases, crudes are processed at temperatures within the
range of 600-1000.degree. F.
Furthermore, upon heating or subjecting the crude oil to various catalytic
processes, the impurities are converted more completely to volatile and
water-soluble compounds. Examples of these are: HCl; CO; CO.sub.2;,
formic, acetic and other volatile carboxylic acids; H.sub.2 S; SO.sub.2 ;
SO.sub.3 and NH.sub.3. Besides NH.sub.3, other basic compounds, especially
monoethanolamine, diethanolamine, etc. can be present because of the
rerouting of various refinery "slop" streams for reprocessing. In
catalytic units, more NH.sub.3 and H.sub.2 S are formed relative to the
stronger inorganic and organic acids than in simple distillation
equipment. Thus the composition and pH of the corrosive aqueous phase can
vary substantially and be dependent upon crude oil contaminants and
processing. Furthermore, the pH within a given system will change as water
condensation proceeds due to the different distribution function of the
volatile species among hydrocarbon, aqueous and vapor phases.
In FCC units and certain crude units, aqueous condensates can be alkaline
in nature Data for many conventional corrosion inhibitors show that
significantly high treatment levels are required for corrosion protection
of ferrous and non-ferrous containers in high pH, sulfidic environments
The use of such high treatment levels is economically unattractive.
This is especially true for admiralty brass and would be expected to be
true for other copper alloys (e.g., cupronickels). This phenomenon is a
result of the stability of copper/ammonia (or amine) complexes. At high pH
(above 7.0), the amines convert from cationic to neutral forms with a
corresponding increased propensity to complex copper ions in solution This
accelerates corrosion by removal of the metal atoms and corrosion products
The present invention has particular utility in overhead condensing systems
of various refinery and petrochemical processing units. Usually the units
themselves and their associated piping are of sufficient thickness to
provide many years of service under general corrosive attack. In these
units, however, tower trays and heat exchanger tubes are relatively thin
due to weight constraints or to allow high rates of heat transfer. Thus,
these components are subject to shorter service life, especially if
localized corrosion, such as underdeposit corrosion, occurs. This is more
likely to occur in alkaline systems where various ammonia or amine salts
can form deposits leading to localized attack. The tubes are usually made
of mild steel due to the low cost of this metal, but admiralty brass and
cupronickel are frequently used. In extremely aggressive systems titanium
heat exchanger bundles have been used.
Besides corrosion inhibition, another desirable property of any inhibitor
is substantial solubility in the hydrocarbon fluids being treated. Lack of
sufficient solubility can lead to deposition or plugging problems. The
inhibitors are usually fed as concentrated solutions (percent levels) into
a stream which is primarily vapor and of high temperature. The inhibitor
must stay soluble under these conditions in order to contact and film the
metal parts and to prevent agglomeration and deposition. This is
particularly important in catalytic units which produce light hydrocarbon
products. As discussed above, the formation of deposits on thin parts such
as exchanger tubes can lead to frequent leaks and downtime due to
underdeposit corrosion or physical blockage A further effect of such
deposits is to impede heat transfer. Since most corrosion inhibitors
contain amine functionality, they can be aggressive to copper alloys.
Also, because these inhibitors partition to the oil phase in preference to
water, they are returned to the tower via reflux streams. As the reflux
vaporizes, insufficient solubility of the filmer will result in deposition
on tower trays. Accumulation of such deposits will interfere with
establishment of vapor-liquid equilibria within the tower and cause
excessive pressure drops within the tower.
The present invention combines both excellent corrosion inhibition and
increased hydrocarbon solubility properties.
SUMMARY OF THE INVENTION
We have found that certain hydrocarbon soluble polyamidoamines derived from
tallowtriamine or tallowtetramine exhibit superior mild steel and
admiralty brass corrosion inhibition under alkaline conditions even at
surprisingly low concentrations. This is quite unexpected since other
polyamidoamines derived from oleyldiamine or even tallowdiamine do not
provide such protection at the low concentration levels tested. In fact,
the tallowtriamine and tallowtetramine reaction products of the invention
were compared with a commercially available complex polyamidoamine and
with an alkyl imidazoline corrosion inhibitor and were found capable of
providing superior protection at lower treatment dosages than those needed
for commensurate protection by the aforementioned commercially available
corrosion inhibitors.
PRIOR ART
Polyamidoamines are not new. A multiplicity of same are disclosed in U.S.
Pat. No. 3,445,441 (Rushton) and are generically described therein as
being formed via reaction of a polyamine and acrylate compounds such as
methylacrylate compounds (e.g., methylacrylate and other lower alkyl
esters of acrylic acid). However, the specific polyamidoamines of the
present invention are not specifically mentioned.
The Rushton patent discloses a myriad of uses for the polyamidoamines. For
instance, the patent states that they be used, inter alia, as emulsion
breakers, corrosion inhibitors for metals, "most particularly iron, steel
and ferrous alloys" (Col. 14, lines 16-17), water clarifiers, flocculants,
etc. Rushton is silent with respect to use of the specific hydrocarbon
soluble tallowtriamine/tallowtetramine based polyamidoamines herein
disclosed and claimed to inhibit alkaline corrosion of mild steel and
admiralty brass. Rushton tested his reaction products under acidic
conditions where most known inhibitor compounds are effective. In
contrast, in accordance with the present invention, effective corrosion
inhibition is accomplished even under the highly alkaline conditions noted
above.
Also of possible interest to the invention are: U.S. Pat. No. 4,131,583
(Boerwinkle, et al.) which discloses corrosion inhibiting compositions
combining (1) a salt of carboxylic acid and organic amine and (2) water
dispersible polymers; U.S. Pat. No. 3,397,152 (Brown, et al.) which
discloses the use of aryl stearic amines as corrosion inhibitors., U.S.
Pat. No. 3,412,024 (Stanford) disclosing alkyl benzene sulfonic acid salts
of partial amides of organic polyamines and certain organic acids; and
U.S. Pat. No. 3,404,165 (Budde, et al.).
DETAILED DISCLOSURE
The corrosion inhibitors of the invention are hydrocarbon soluble reaction
products of (1) tallowtriamine or tallowtetramine and (2) an acrylic acid
compound having the formula:
##STR1##
wherein R=H or CH.sub.3 and R' is methyl, ethyl, propyl, isopropyl, butyl,
amyl, or hexyl (i.e., branched or straight chain C.sub.1 - C.sub.6 alkyl).
Based upon laboratory tests, the presently preferred reaction product is a
polyamidoamine made with tallowtetramine or tallowtriamine and
methylacrylate in a 1:1 molar ratio.
The reaction products may be formed via the preparatory route outlined at
Column 3, lines 3-39, of the aforementioned Rushton patent; the entire
disclosure of which is hereby incorporated by reference.
Accordingly, the polymerization reaction may be carried out at temperatures
up to 200.degree. C. and even higher. Generally, the reactants are first
heated below 100.degree. C., such as at 80-90.degree. C., for a suitable
period of time, such as a few hours. Since the tallowtriamines and
tallowtetramine reactants are preferably to be reacted with
methylacrylate, the progress of the reaction can be determined by the
removal of CH.sub.3 OH in forming the amide. During the early part of the
reaction, alcohol may be quite readily removed from the reaction mixture
at temperatures below 100.degree. C. As the reaction slows, the
temperature is raised to accelerate the polymerization to completion. The
temperature may be raised to 150-200.degree. C. toward the end of the
reaction. Removal of the alcohol (CH.sub.3 OH when methylacrylate is used)
is a way of determining the progress and completion of the reaction.
Generally, the molar ratios of the (1) tallowtriamine and/or
tallowtetramine reactant to the (2) acrylic acid type reactant may vary
within a range of a (1):(2) of 1:2 to 2:1. The presently preferred
tallowtriamine and/or tallowtetramine-methylacrylate reaction product is
prepared by an equimolar concentration of the two reactants.
In addition to the above reactants, (3) alkylenepolyamines such as those
having from about 3-10 amino groups and from about 2-6 carbon alkylene
groups may be incorporated into the polymeric matrix via conventional
techniques. When such alkylenepolyamine addition is desired,
triethylenetetramine is presently preferred. When this third reactant (3)
is employed, the molar ratios of components (1):(2):(3) may be within the
range of 1:0.5-2.0:0.5-2.0.
The reaction product may be coated on the metal substrate for which
protection is desired by pretreatment of the metal surface or by
continuous addition to the corrosive fluids. Generally, the hydrocarbon
soluble tallowtriamine/tallowtetramine reaction products may be admitted
to the hydrocarbon medium in an amount of about 0.5-500 parts reaction
product to one million parts hydrocarbon. From an economical point of
view, it is desirable to add only about 0.5-50 parts of the corrosion
inhibitor. This low addition range provides one of the distinct advantages
of the invention in that superior metal corrosion inhibition is effected
at low, economical feedrates even under alkaline conditions.
It should be understood herein that the term hydrocarbon is herein used in
its broadest generic sense covering all petroleum rock oils, corrosive
crudes, crudes in various stages of refining, and petrochemicals
generally.
The following examples are presented for purposes of illustration only and
are not to be construed as to limit the invention.
EXAMPLES
In order to ascertain the effectiveness of the hydrocarbon soluble
methylacrylate-tallowtriamines and methylacrylate-tallowtetramines of the
present invention in inhibiting corrosion of metals in alkaline
environments, a series of polyamidoamines based on tallow di, tri, and
tetramines were prepared as described earlier and were evaluated using the
conditions outlined below.
TEST PROCEDURES
Two procedures were used to evaluate corrosion inhibitors under alkaline
conditions. The conditions are similar to those encountered in an FCC unit
condensation system. As discussed above, alkaline corrosion can also occur
in crude oil distillation towers depending on crude oil source and
operating conditions.
Metallic coupons are cleaned by conventional cleaning methods. After
rinsing with distilled water and isopropanol, the coupons are dried and
weighed. Corrosion tests are conducted with a 2:1 brine to hydrocarbon
ratio at about 150.degree. F. on a "corrosion wheel" for several hours.
The brine consists of NH.sub.4 Cl and (NH.sub.4).sub.2 S in distilled
water. For admiralty brass tests the brine pH is adjusted to 9.1 with
addition of NH.sub.4 OH. The mild steel brine pH is adjusted to 7.7 with
HCl. After the test exposure, coupons are cleaned by conventional methods.
After rinsing as above, coupons are dried and weighed.
Evaluation of performance is by percent protection, defined as:
##EQU1##
For ease of comparison, examples of the present invention are numbered,
whereas comparative examples have been assigned letter designations.
COMPARATIVE EXAMPLE A
The product of the reaction of an equimolar ratio of tallowdiamine and
methylacrylate was found to have an average molecular weight of 970 g/mol
and contained 6.9% nitrogen by weight. When tested as a corrosion
inhibitor for admiralty brass using the conditions described above, an
average protection of 15% was achieved when the inhibitor was added at a
concentration of 5.0 ppm by volume.
COMPARATIVE EXAMPLE B
0.5 moles of tallowdiamine and 0.5 moles HPA-2* were reacted with 1 mole of
methylacrylate. The resulting complex polyamidoamine product had an
average molecular weight of 490 g/mol and a nitrogen content of 15.6%.
When this synthesized corrosion inhibitor was tested at a concentration of
2.5 ppm under conditions described above for admiralty brass, an average
protection level of 26% was achieved.
*HPA-2 complex mixture of ethyleneamines containing derivatives with six or
more nitrogen atoms per molecule -- available Union Carbide Corporation.
COMPARATIVE EXAMPLE C
0.5 moles of oleyldiamine and 0.5 moles of HPA-2 were reacted with 1 mole
of methylacrylate. The resulting product had an average molecular weight
of 550 g/mol and had a nitrogen content of 15.6% by weight. This reaction
product was tested as a corrosion inhibitor for admiralty brass under the
conditions given above and an average protection of 7% was achieved when
added at a concentration of 2.5 ppm by volume.
COMPARATIVE EXAMPLE D
1 mole of HPA and 1 mole of methylacrylate were reacted. The resulting
product had an average molecular weight of 630 g/mol and contained 24.0%
nitrogen by weight. When this synthesized corrosion inhibitor was tested
at a concentration of 10 ppm under conditions described above for
admiralty brass, an average protection of 43% was achieved.
COMPARATIVE EXAMPLE E
OFC-1180* was tested as a corrosion inhibitor under the conditions
described above for admiralty brass. Average protection levels of 28% and
40% were determined when added at concentrations of 1.0 and 2.5 ppm, by
volume, respectively.
*OFC-1180, available Chemlink Petroleum, Inc., polyimido amine estimated MW
of 605 g/mol with a nitrogen content of approximately 6.9% by weight.
COMPARATIVE EXAMPLE F
When CI-llC, an imidazoline based corrosion inhibitor commercially
available from Betz Process Chemicals, Inc., was used as a corrosion
inhibitor of admiralty brass under the conditions described above, average
protection levels of 12%, 38%, 52% and 80% were determined when added at
concentrations of 1.0, 2.0, 4.0 and 10 ppm, respectively.
EXAMPLE 1
The product of the reaction of an equimolar ratio of tallowtriamine and
acrylic acid was determined to have an average molecular weight of 520
g/mol and contained 9.0% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0, 5.0 and 10 ppm,
under conditions described above for admiralty brass, average protection
levels of 27%, 59% and 66% were determined, respectively.
EXAMPLE 2
The product of the reaction of an equimolar ratio of tallowtriamine and
methylacrylate was determined to have an average molecular weight of 920
g/mol and contained 8.9% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0, 5.0 and 10 ppm
under conditions described above for admiralty brass, average protection
levels of 51%, 56% an 64% were determined, respectively.
EXAMPLE 3
The product of the reaction of an equimolar ratio of tallowtriamine and
methylacrylate was determined to have an average molecular weight of 1160
g/mol and contained 8.9% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 36% and 49% were determined, respectively.
EXAMPLE 4
The product of the reaction of an equimolar ratio of tallowtriamine and
methylacrylate was determined to have an average molecular weight of 1460
g/mol and contained 8.9% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 46% and 47% were determined, respectively.
EXAMPLE 5
The product of the reaction of an equimolar ratio of tallowtriamine and
methylacrylate was determined to have an average molecular weight of 1640
g/mol and contained 8.9% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 35% and 43% were determined, respectively.
EXAMPLE 6
The product of the reaction of an equimolar ratio of tallowtetramine and
methylacrylate was determined to have an average molecular weight of 730
g/mol and contained 11.3% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 41% and 70% were determined, respectively.
EXAMPLE 7
The product of the reaction of an equimolar ratio of tallowtetramine and
methylacrylate was determined to have an average molecular weight of 900
g/mol and contained 11.3% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 40% and 51% were determined, respectively.
EXAMPLE 8
The product of the reaction of tallowtetramine and methylacrylate when
added in a 1:1.5 ratio was determined to have an average molecular weight
of 1490 g/mol and contained 10.7% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 41% and 65% were determined, respectively.
EXAMPLE 9
The product of the reaction of an equimolar ratio of tallowtetramine and
methylacrylate was determined to have an average molecular weight of 1730
g/mol and contained 11.3% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 29% and 48% were determined, respectively.
EXAMPLE 10
The product of the reaction of tallowtetramine and methylacrylate when
added in a 1:2 ratio was determined to have an average molecular weight of
2500 g/mol and contained 10.2% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 37% and 64% were determined, respectively.
EXAMPLE 11
The product of the reaction of tallowtetramine and methylacrylate when
added in a 1:2 ratio was determined to have an average molecular weight of
3000 g/mol and contained 10.2% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0 and 2.5 ppm under
conditions described above for admiralty brass, average protection levels
of 22% and 57% were determined, respectively.
EXAMPLE 12
Tallowtetramine (0.5 mol) and triethylenetetramine. (0.5 mol) were reacted
with 1.0 mole methylacrylate. The resulting polyamidoamine had an average
molecular weight of 700 g/mol and a nitrogen content of 14.0% by weight.
When this synthesized corrosion inhibitor was tested at concentrations of
1.0 and 2.5 ppm under conditions described above for admiralty brass,
average protection levels of 48% and 62% were determined, respectively.
EXAMPLE 13
0.5 mole tallowtetramine and 0.5 mole triethylenetetramine were reacted
with 1.0 mole methylacrylate. The resulting polyamidoamine, having an
average molecular weight of 630 g/mol and 16.1% nitrogen, was obtained.
When the synthesized corrosion inhibitor was tested under the admiralty
brass conditions expressed above at a concentration of 2.5 ppm, an average
protection level of 58% was determined.
EXAMPLE 14
0.5 mole tallowtetramine and 0.5 mole triethylenetetramine were reacted
with 1 mole of methylacrylate. The resulting polyamidoamine had an average
molecular weight of 960 g/mol and a nitrogen content of 16.1%. When the
synthesized corrosion inhibitor was tested at a concentration of 2.5 ppm
under the admiralty brass conditions above expressed, an average
protection level of 30% was determined.
EXAMPLE 15
0.5 mole tallowtetramine and 0.5 mole triethylenetetramine were reacted
with 1 mole of methylacrylate. The resulting polyamidoamine had an average
molecular weight of 980 g/mol and a nitrogen content of 16.1%. When this
synthesized corrosion inhibitor was tested at a concentration of 2.5, an
average protection level of 19% for admiralty brass was determined.
EXAMPLE 16
1 mole of tallowtetramine was reacted with 1 mole of acrylic acid to yield
a product containing 11.4% nitrogen by weight. When tested in accord with
the admiralty brass inhibition procedures supra, an average of 31%
protection was afforded when 2.5 ppm of the reaction product was used.
EXAMPLE 17
1 mole of tallowtetramine was reacted with 1 mole of acrylic acid to yield
a product containing 11.4% nitrogen by weight. When tested in accord with
the admiralty brass inhibition procedures supra, an average of 41%
protection was afforded when 2.5 ppm of the reaction product was used.
A summary of the admiralty brass corrosion inhibition tests is given in
Table I.
The following examples were undertaken to determine the efficacy of the
present invention in inhibiting corrosion of mild steel under alkaline
conditions. As per above, examples of the present invention are numbered,
whereas comparative examples have been given letter designations.
TABLE I
__________________________________________________________________________
Percent Protection
1.0 2.5 5.0 10
Example
Amine Acrylate
Ratio
% N
ppm ppm ppm ppm
__________________________________________________________________________
A Tallowdiamine
Methylacrylate
1:1
6.9 15(2)
B Tallowdiamine and
Methylacrylate
1:1
15.6 26(2)
HPA-2 ( 1:1)
C Oleyldiamine and
Methylacrylate
1:1
15.6 7(2)
HPA-2 ( 1:1)
D HPA-2 Methyacrylate
1:1
24.0 43(2)
E OFC-1180 6.9
28(10)
40(8)
F CI-11C 12(2)*
38(2)
52(2)
80(2)
** ***
1 Tallowtriamine
Acrylic Acid
1:1
9.0
27(2) 59(2)
66(2)
2 Tallowtriamine
Methylacrylate
1:1
8.9
51(2) 56(2)
64(2)
3 Tallowtriamine
Methylacrylate
1:1
8.9
36(2)
49(1)
4 Tallowtriamine
Methylacrylate
1:1
8.9
46(2)
47(2)
5 Tallowtriamine
Methylacrylate
1:1
8.9
35(2)
43(2)
6 Tallowtetramine
Methylacrylate
1:1
11.3
41(7)
70(4)
7 Tallowtetramine
Methylacrylate
1:1
11.3
40(2)
51(2)
8 Tallowtetramine
Methylacrylate
1:1.5
10.7
41(7)
65(4)
9 Tallowtetramine
Methylacrylate
1:1
11.3
29(2)
48(2)
10 Tallowtetramine
Methylacrylate
1:2
10.2
37(6)
67(4)
11 Tallowtetramine
Methylacrylate
1:2
10.2
22(2)
57(4)
12 Tallowtetramine and
Methylacrylate
.5:.5:1
14.0
48(5)
62(4)
triethylenetetramine
(1:1)
13 Tallowtetramine and
Methylacrylate
.5:.5:1
16.1 58(3)
triethylenetetramine
(1:1)
14 Tallowtetramine and
Methylacrylate
.5:.5:1
16.1 30(3)
triethylenetetramine
15 Tallowtetramine and
Methylacrylate
.5:.5:1
16.1 19(3)
triethylenetetramine
16 Tallowtetramine
Acrylic acid
1:1
11.4 31(2)
17 Tallowtetramine
Acrylic acid
1:1
11.4 41(2)
__________________________________________________________________________
* = 1.5 ppm
** = 2.0 ppm
*** = 4.0 ppm
COMPARATIVE EXAMPLE G
When OFC-1180 was tested as a corrosion inhibitor using the conditions
described above for mild steel, average protection levels of 2% and 98%
were determined when added at concentrations of 2.5 ppm and 5.0 ppm by
volume, respectively.
COMPARATIVE EXAMPLE H
When CI-llC was used as a corrosion inhibitor for mild steel under the
conditions described earlier, average protection levels of 17%, 93%, 96%
and 96% were determined when added at concentrations of 10, 12.5, 15 and
20 ppm, respectively.
EXAMPLE 18
The product of the reaction of an equimolar ratio of tallowtriamine and
methylacrylate was determined to have an average molecular weight of 1770
g/mol and contained 8.9% nitrogen by weight. When this synthesized
corrosion inhibitor was tested at concentrations of 1.0, 2.5, 5.0 and 10
ppm under the conditions described above for mild steel, average
protection levels of 12%, 56%, 95% and were determined, respectively.
EXAMPLE 19
The product of the reaction of an equimolar ratio of tallowtriamine and
methylacrylate was determined to have an average molecular weight of 1710
g/mol and contained 8.9% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 1.0, 2.5, 5.0 and 10
ppm under the conditions described above for mild steel, average
protection levels of 4%, 79%, 98% and 97% were determined, respectively.
EXAMPLE 20
The product of the reaction of an equimolar ratio of tallowtetramine and
methylacrylate was determined to have an average molecular weight of 1970
g/mol and contained 11.3% nitrogen by weight. When this synthesized
corrosion inhibitor was tested at concentrations of 1.0, 2.5, 5.0 and 10
ppm under the conditions described above for mild steel, average
protection levels of 29%, 94%, 99% and 97% were determined, respectively.
EXAMPLE 21
The product of the reaction of an equimolar ratio of tallowtriamine and
methylacrylate was determined to have an average molecular weight of 1460
g/mol and contained 8.9% nitrogen by weight. When the synthesized
corrosion inhibitor was tested at concentrations of 2.5 and 5.0 ppm under
the conditions described above for mild steel, average protection levels
of 77% and 99% were determined, respectively.
The mild steel corrosion inhibition results are summarized in Table II.
TABLE II
__________________________________________________________________________
Percent Protection
1.0
2.5
5.0
10 12.5
15
Example
Amine Acrylate
Ratio
% N
ppm
ppm
ppm
ppm
ppm
ppm
__________________________________________________________________________
OFC-1180* 6.9 2(2)
98(2)
CI-11C** 17(2)
93(2)
96(2)
Tallowtriamine
Methyacrylate
1:1 8.9
12(2)
56(2)
95(2)
97(2)
Tallowtriamine
Methyacrylate
1:1 8.9
4(2)
79(2)
98(2)
97(2)
Tallowtetramine
Methyacrylate
1:1 11.3
29(2)
94(2)
99(2)
97(2)
Tallowtetramine
Methyacrylate
1:1 11.3
44(2)
95(2)
98(2)
Tallowtetramine
Methyacrylate
1:1 11.3
33(2)
79(2)
97(2)
Tallowtriamine
Methyacrylate
1:1 8.9 77(2)
99(2)
__________________________________________________________________________
*A mixture of polyamidoamines commercially available from Chemlink, Inc.
**A commercially available imidazoline based corrosion inhibitor from Bet
Process Chemicals, Inc.
SOLUBILITY STUDIES
In order to access the solubility of the tallowtriamine/tetramine reaction
products of the present invention, solubility studies in heptane and
pentane solutions were undertaken. Results appear in Table III.
TABLE III
______________________________________
Solubility in Heptane or Pentane
When Added at Concentration of 5,000 ppm
Inhibitor Heptane Solubility
Pentane Solubility
______________________________________
Tallowtetramine
Material is soluble, no
Material is soluble, no
methylacrylate
cloudiness or precipi-
cloudiness or precipi-
1:1 molar ratio
tate tate
11.3% N
CI-11C Material is soluble, no
Material is soluble, no
cloudiness or precipi-
cloudiness or precipi-
tate tate
OFC-1180 Material not soluble,
Material not soluble,
heptane solution
pentane solution
cloudy, tacky inhibitor
cloudy, tacky inhibitor
deposit on bottom and
deposit on bottom and
sides of containers
sides of containers
Tallowtetramine
Material is not soluble
Material is not soluble
but precipitate is not
but precipitate is not
tacky and disperses
tacky and disperses
upon agitation upon agitation
______________________________________
The solubility tests are significant as they demonstrate that the
tallowtetramine/methylacrylate reaction product exhibits superior
hydrocarbon solubility in comparison with the OFC-1180 product.
Accordingly, use of the specific tallowtetramine/tallowtriamine based
polyamidoamines of the present invention will be less likely to cause
deposition, fouling and plugging than the 1180 material in hydrocarbon
mediums. Since the tallowtetramine/methylacrylate polyamidoamine of Table
III is totally soluble in both pentane and heptane at a concentration of
5,000 ppm, the present invention provides significant improvement over
many conventional inhibitors which are efficient for alkaline sour
corrosion. Although the imidazoline, CIllC, has appreciable pentane and
heptane solubility, it is a very inefficient alkaline sour corrosion
inhibitor.
While the invention has been described hereinabove with respect to specific
embodiments of same, such are not intended to limit the scope of the
invention. The invention is intended to cover any equivalents,
modifications, etc., and is intended to be limited solely by the scope of
the appended claims.
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